Acts 12:3

ESV and when he saw that it pleased the Jews, he proceeded to arrest Peter also. This was during the days of Unleavened Bread.
NIV When he saw that this met with approval among the Jews, he proceeded to seize Peter also. This happened during the Festival of Unleavened Bread.
NASB When he saw that it pleased the Jews, he proceeded to arrest Peter as well. (Now these were the days of Unleavened Bread.)
CSB When he saw that it pleased the Jews, he proceeded to arrest Peter too, during the Festival of Unleavened Bread.
NLT When Herod saw how much this pleased the Jewish people, he also arrested Peter. (This took place during the Passover celebration. )
KJV And because he saw it pleased the Jews, he proceeded further to take Peter also. (Then were the days of unleavened bread.)

What does Acts 12:3 mean?

"He" is Herod Agrippa I, the grandson of Herod the Great and the king of most of his territory. His reign started in the tetrarchy northeast of Galilee, but his kingdom spread, encompassing Judea and Samaria from AD 41 until his death in AD 44. "The Jews" mentioned here may mean the citizens, but it was also a commonly used reference for the Sanhedrin—John's gospel uses this terminology. The Sanhedrin is the ruling council of Jews, composed of priests, elders, and scribes. "Scribes" are experts in the Law and can come from the Sadducees or the Pharisees; Agrippa is particularly friendly with the Pharisees.

Agrippa arrested the apostle James, the brother of John and son of Zebedee, and beheaded him (Acts 12:1–2). It's unclear why. At the beginning of the church, the apostles clashed with the Sanhedrin, and Saul gained approval from the Sanhedrin to persecute Jesus-followers after foreign-born Jews argued with and murdered Stephen (Acts 6:8—8:3; 9:1–2). But since Saul's conversion, the church has enjoyed relative peace (Acts 9:1–31). To this point, it seems the Roman government has completely ignored the church as a new sect of Judaism that hasn't caused any political trouble.

Agrippa surely knows some of this, but there's no indication it influences his treatment of James. Agrippa is friendly with the Sanhedrin, in part because he protected the temple from the installation of Caligula's statue. He also reads parts of the Mosaic law in public. We don't know, however, why Agrippa would take a disliking to James.

Politically, it turns out to be a good move for him. The Sanhedrin is pleased. In order to bolster the connection even more, he arrests Peter. But it is the "days of Unleavened Bread"—the week after Passover. Only the first and last days of the Feast of Unleavened Bread are holy Sabbaths, in addition to any normal weekly Sabbath that falls in the timeframe (Exodus 12:16). It wouldn't be against the law for Agrippa to have Peter killed, but it would be unseemly to execute someone while the Jews celebrate their rescue from Egypt.
What is the Gospel?
Download the app: